<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }
        
        .bck {
            text-align: center;
        }
        
        .box {
            margin: 0 auto;
            width: 100px;
            height: 100px;
            background-color: #000;
        }
    </style>
</head>

<body>
    <div class="bck">
        <button onclick="click1()">变宽</button>
        <button onclick="click2()">变高</button>
        <button onclick="click3()">变色</button>
        <button onclick="click4()">影藏</button>
        <button onclick="click5()">重置</button>
        <div class="box">

        </div>
    </div>

</body>
<script>
    let div = document.querySelector('.box')

    function click1() {
        div.style.width = "500px"
    }

    function click2() {
        div.style.height = "500px"
    }

    function click3() {
        div.style.backgroundColor = "red"
    }

    function click4() {
        div.style.display = "none"
    }

    function click5() {
        div.style = ""
    }
</script>

</html>